The function of a turbine engine air intake duct, in particular an aircraft turbine engine intake duct, is to guide the air from the air intake of the turbine engine to the gas generator. Some turbine engines, such as a turboprop engine or a non-ducted propeller engine (for example of the type having a counter-rotating doublet), can comprise an air intake in the turbine engine which has a different axis to the air intake in the gas generator that drives the propeller. Their axes can be offset. This is generally the case for a turboprop engine in which the axis of the propeller is itself offset with respect to that of the gas generator. This may also be the case in an engine having a counter-rotating doublet at the front of the engine. FIG. 1 shows a turbine engine of this type having two air intakes having axes offset with respect to that of the turbine engine. The air intake conduit thus comprises a region in which the air flow undergoes significant deflection.
In this case, the air intake duct comprises a relatively complex-shaped intermediary portion between the air intake and the gas generator, which portion optionally comprises a channel for discharging particles which forms a sink, extends substantially in the direction of the axis of the air intake in the nacelle and allows for foreign bodies to be discharged so that they do not get into gas generator.
Seen from the side, the intermediary portion has a general goose neck shape of which the upstream end is connected to the air intake in the nacelle and of which the downstream end is connected to the air intake in the gas generator by means of a supply channel. The supply channel is located radially inward with respect to the discharge channel, and the intermediary portion comprises a part for connecting one channel to the other. There are other types of air intake, each of these air intakes comprising a connecting part that forms a deflection of the air flow.
The function of the air intake duct is to supply the gas generator with air in the most homogenous manner possible. However, the complex shape of the aforementioned duct brings about distortions in the air flow that supplies the gas generator, which has a negative impact on the performance and operability of the turbine engine. Said distortion is substantially due to the shedding of air owing to the significant deflection of the air flow in the aforementioned intermediary portion.
A solution to this problem would be to incorporate vortex or eddy generators at the upstream end of the air intake duct in order to energize the boundary layer and reduce shedding. This could, for example, involve transposing passive devices that use means of producing eddies to control the shedding of air on turbine engine blades. FR 2976634, which is in the name of the present applicant, describes a device of this type. Unfortunately, it appears that this solution, though functional, would not be effective enough in this type of design. Indeed, the duct opens very widely in the region of the deflection, and the disturbances necessary for limiting shedding of the boundary layer cannot be provided by a device of this type.
Another solution known from the prior art comprises a system for actively controlling shedding of the boundary layer in air intake ducts having significant deflections. For example, there are known devices in which the air circulating in the duct is sucked up or air is injected at very high speeds. However, devices of this type are complex and require elements for circulating the air, by means of suction or blowing, to be installed in a compartment of the nacelle near to the duct.
To the knowledge of the present applicant, there exists no passive system having eddy generators that produce disturbances sufficient for limiting shedding of the boundary layer in air intake ducts that undergo significant deflections.